Photo Scanning

An optical scanner converts a physical image to a digital image. To capture an image, a scanner divides the image into a grid, and uses a scanning head to record how much light is reflected in each location. Once the computer accumulates this data, it builds a file that represents the image in digital form. Each of the cells in the grid is called a picture element, or pixel.

Scanners used for photographic images should have at least 24 bit color depth (16 million colors) and high dynamic range (the ability to reproduce shadow and brightness details).

Dynamic range is measured on scale from 0.0 (perfect white) to 4.0 (perfect black), and the number for a particular scanner tells how much of that range it can distinguish.

Flatbed Scanner

For scanning prints up to 8 x 10" or even larger, you need a flatbed scanner. Similarly to using a photocopier, you place the photo face down on a glass scanning surface and a scanning head and a sensor array and light source move across the pane, reading the area. Scan prints at 300 dpi (dots per inch) if they will be reproduced at the same size, higher resolution if they will be enlarged, lower resolution of they will be reduced.

Some flatbed scanners include an adapter that allows the scanning of film or transparencies (slides) but the image quality is generally not as good as using a dedicated film scanner.

Film Scanner

Film scanners accept either strips of film or individual slides and pass light through the image rather than reflecting light off of it. Specialized optics and electronics achieve better results when scanning film than flatbed scanners. Because of the small size, film and slides need to be scanned at very high optical resolution. 

Tips for Scanning Prints

• Choose a resolution higher than you need to give you flexibility to enlarge or crop the image. For scanning prints, we recommend 600 dpi.
• Keep the scanner glass clean.
• Carefully clean the print using dry compressed air or a soft brush (see Cleaning and Repair for more information).
• If you are going to do any restoration or enhancement work on the image, save the files using a non-lossy file format such as TIFF. If you are only archiving the files and reduced file size is more important than some loss of picture quality, save JPEG files. 
• Name the files in a useful way, e.g., 1970_Disneyland_Susan.tif rather than Susan27.jpg. 
• When possible, scan more than one image at a time. Most flatbed scanners can automatically separate the images and save them to different files.

Tips for Scanning Negatives or Slides

• Choose a high resolution (3000dpi or above) to uncover as much information in the image as possible.
• Clean the slides using dry compressed air or a soft brush.
• Be careful with automatic slide loaders. A jam can damage your slides.
• Crop the image to eliminate the slide frame or negative edges before you do the final scan. This minimizes the file size and any effect on the automatic contrast and brightness adjustments.
• If available, select the scanner's film profile for the type of film you are scanning, This allows automatic adjustments that save editing time.

Digital Camera

You can also use a digital camera to copy photographs and album pages. This method is particularly useful when copying very large prints.

• If possible, use a copy stand that holds the camera in firm, level position and includes lamps that provide even, shadowless lighting. Failing this, you can use a tripod and indirect daylight (not direct sunlight, which is too harsh).
• Keep the camera lens parallel to the work being photographed (use a small level to check both).
• Set the camera lens to medium range for least edge distortion.
• Set the camera's ISO to the lowest possible setting to maximize picture quality.
• Set the camera to capture the largest image size and best quality possible.
• Switch off the flash.
• Bracket the exposure (take three pictures of each print, one at normal exposure, one with exposure adjustment set to +1 EV, one at -1 EV).